DESCRIPTION (Applicant's abstract): A new experimental strategy for treating ischemia of the human myocardium is to use angiogenic growth factors to induce neovascularization. This approach is based upon recent findings showing that in the adult heart the genes encoding angiogenic growth factors and their receptors are expressed in areas surrounding ischemic myocardium, but at levels that are insufficient to provide robust formation of collaterals. Administration of angiogenic growth factors can be viewed as an amplification of a normal response of the myocardia to ischemia. Vascular endothelial growth factor (VEGF) serves as a major angiogenic factor in normal cardiac development, and its use in therapeutic angiogenesis is currently undergoing clinical evaluation. VEGF binds to two high affinity endothelial cell receptor, KDR and FLT1. The interaction of VEGF with KDR is dependent upon other cell surface molecules, in particular heparan sulfate proteoglycans (NSPG). Little information is available as to the mechanisms by which HSPGs allow for growth factor binding. My application proposes three Specific Aims for clarifying those mechanisms. Specific Aim 1 tests the hypothesis that HSPGs interact with KDR in order to facilitate receptor dimerization and VEGF binding. The proposed experiments build upon previously obtained results that support this hypothesis. Specific Aim 2 is directed at identifying the proteoglycan involved in VEGF binding to KDR. Experiments are proposed for testing whether a known pro teoglycan is responsible; or if not, for purifying the protein and identifying its amino acid sequence. Specific Aim 3 is directed at testing whether the relevant HSPG participates in VEGF-induced signaling events. The rationale for this study relates to the recent information derived from the literature indicating that HSPGs participate in the signal transduction pathways by which cells respond to their extracellular environment.